This invention relates to structures of the type that are employable as a support for equipment, and, more particularly, to a head equipment support structure system that is designed to be cooperatively associated with a nuclear reactor vessel in a nuclear power generation system for purposes of accomplishing the support of equipment that is externally located in the head area of such a vessel.
One of the main operating components of any nuclear power generation system is the nuclear reactor. Commonly, the latter is suitably supported within a pressure vessel. Furthermore, it is within this vessel that the nuclear reaction takes place from which there is generated the energy that is utilized to produce the power that is provided by the nuclear power generation system.
In accord with established practice, the nuclear reactor vessel is in turn suitably housed within an appropriate form of containment structure, the latter commonly being made of concrete. For purposes of effectuating control over the operation of the nuclear reactor housed within the pressure vessel, there is a need to make use of various pieces of equipment. Some of these pieces are designed to be located internally of the vessel with means cooperatively associated therewith for effecting operation thereover from the exterior of the vessel, while others of these pieces are designed to be physically located externally of the vessel with means cooperable therewith extending into the vessel interior. In either case, however, all of the equipment is generally to be found located within the confines of the containment structure. Normally, in addition to such pieces of equipment, instrumentation is made use of for purposes of monitoring the activities taking place within the vessel. Thus, such instrumentation constitutes yet another form of means for which support must be provided in the immediate vicinity over the vessel. In summary, therefore, it should be readily apparent from the above that normally it is to be expected that there will be found a multiplicity of various pieces of equipment as well as various types of instrumentation extending outwardly from the vessel for which a need exists to provide support therefor.
Insofar as regards this matter of providing support for the aforementioned equipment and/or instrumentation, there are a number of factors that must be borne in mind in arriving at a decision as to the nature of the support that should be utilized. More specifically, reference is had here to the fact that consideration must be given to much more than merely a selection of simply any given one of the many commonplace forms of support means that have been known to have been used heretofore by the prior art. For example, there is a need to consider the nature of the environment in which the subject equipment and/or instrumentation is being employed, and the potential for deleterious effects that such an environment may have on the ability of a given form of support means to provide the support deemed to be required therefrom. Moreover, it is of prime importance that consideration be given to the matter of safety. In addition, with regard to all of the above, there is the still further need to take cognizance of the fact that there exists various rules and regulations that have been promulgated by governmental agencies relating to this subject. Lastly, because of relatively recent incidents that have occurred involving nuclear power generation systems, other steps have been suggested for implementation looking towards the effectuation of additional improvements in the practices and procedures that it is recommended be followed in the course of constructing and operating each of the many components normally thought of being encompassed within a conventionally constructed nuclear power generation system.
In order to effect the requisite degree of communication between the interior and the exterior of the nuclear reactor vessel for purposes of accomplishing the operation of the various pieces of equipment and instrumentation associated with the proper functioning of the nuclear reactor housed within and outside the reactor vessel, one of the means most frequently employed for this purpose is one form or another of cabling. The vast usage which is made of cabling in this regard creates the image of a virtual maze thereof within the confines of the containment structure directly over the reactor vessel. As such, there exists an obvious need to furnish some form of support therefor in order to provide effective separation therebetween for ease of ready identification thereof, etc. This need is further compounded by the fact that in many instances the use of redundant cabling is mandated by safety rules and/or regulations, or may be employed simply as a matter of prudent practice. Thus, there is a requirement for more than mere separation of such cabling. Namely, that cabling which may be viewed as constituting the primary set of cabling must be effectively isolated from the cabling which functions as a backup thereto such that the likelihood, that damage occasioned from the same source will be done concurrently to both the primary and the backup cabling, is very improbable. By way of further illustration of this point, sufficient separation and isolation of the backup cabling from the primary cabling should exist such that in the event that the latter is damaged, as for instance by fire, the probability that the backup cabling would suffer damage also from the same fire would be extremely remote.
Apart from the functional requirements enumerated above which should be satisfied by any support structure that is selected for use in association with the reactor vessel of a nuclear power generation system, there are other attributes which such a support structure should possess. For example, means must be provided to enable access to be had periodically to the interior of the containment structure for purposes of effecting repairs and/or the carrying out of normal maintenance on the equipment housed therewithin. This encompasses the need to replace or repair the aforementioned cabling. Consequently, access must obviously be available thereto. In addition, such cabling should be provided with suitable connection means at the termination points thereof so as to enable the cabling to be readily disconnected for purposes of effecting the replacement thereof, etc.
Moreover, besides the need to simply gain access to the interior of the containment structure, there also exists a need to periodically remove the head of the reactor vessel for purposes of exposing the interior thereof such as, for instance, to effectuate the performance of the refueling of the nuclear reactor. Accordingly, whatever form of support structure is selected for utilization within the containment structure for purposes of providing support for the pieces of equipment and/or instrumentation associated with the operation of the nuclear reactor must be suitably located or must embody the capability of being positioned so as to not impede the removal of the reactor vessel head. In this context, the support structure should be sufficiently movable to enable the removal of the head of the reactor vessel to be accomplished in an expeditious manner. A further complication in this regard, however, is the fact that a considerable amount of ductwork is to be found cooperatively associated with the reactor vessel, as well as a structure which is referred to by those skilled in this art as a missile shield. The existence of both this ductwork and the missile shield impose restrictions on the degree of accessibility that is afforded to the aforesaid support structure as well as function to limit the extent to which the subject support structure may be moved for purposes of effecting removal of the reactor vessel head.
Essentially, the function of the ductwork that has been referred to above is to afford a means of funneling to the reactor vessel the cooling required in the course of the conduct of the operation of the nuclear reactor housed within the reactor vessel. The missile shield, on the other hand, referred to above commonly takes the form of a concrete member. The function thereof is to form a barrier in the event that an incident should occur whereby members confined within the containment structure are given impetus such that they take on the characteristics of missiles. Thus, the concrete missile shield is designed under such circumstances to absorb the kinetic energy possessed by such missile-like members such as to cause them to slow down, i.e., loose their potential to cause damage within the interior of the containment structure and/or to escape from the containment structure whereby they would pose a danger to personnel and equipment located externally of the containment structure.
The need to periodically effect the refueling of the nuclear reactor housed within the reactor vessel has been alluded to hereinabove. With further regard thereto, it is important that this task be accomplished in a safe, yet timely fashion. Namely, it is important that the overall time required to perform the refueling operation be kept at a minimum inasmuch as during this period, the nuclear power generation system of which the nuclear reactor is a principal component is not producing power. Moreover, inasmuch as the nuclear reactor is housed within an environment which, if proper safeguards are not taken, can be hazardous to humans, it is important that the refueling operation be completed in a minimum of time. Accordingly, irrespective of what may occasion the need to shutdown the nuclear reactor, i.e., the need to refuel the latter, etc., it is important that the period during which a power outage occurs be kept to a minimum, both because of the effect that the power loss has on the customers of the power generation system as well as because of the desire to minimize the time during which the personnel working in the vicinity of the reactor are exposed to the potentially hazardous environment represented thereby. Thus, a further important consideration in selecting a support structure for use in cooperative association with the reactor vessel is that the structure which is selected for use should not have an adverse impact on the ability to effect a minimization of the time period during which the nuclear power generation system is in a non-power producting state. On the other hand, if further time-savings in this regard are achievable through the employment of a given support structure, this would enhance the desirability of making use of the latter.
Yet another consideration that should be borne in mind in the course of determining the nature of the support structure that will be selected for use in effecting the separation and support of the pieces of equipment, instrumentation and cabling utilized in connection with the operation of the nuclear reactor housed within the reactor vessel is the ability thereof to be employed in retrofit situations. Namely, it would be desirable to have provided a form of support structure that is usable not only in new installations, but also is equally applicable for use in existing installations for purposes of effecting improvements over the support structures that are presently to be found employed therein.
It is, therefore, an object of the present invention to provide a support structure system that is particularly suitable for use in cooperative relation with a reactor vessel in a nuclear power generation system for purposes of providing support for the head equipment associated therewith.
It is another object of the present invention to provide such a head equipment support structure system that is operable in the manner of a cable support structure.
It is still another object of the present invention to provide such a head equipment support structure system that, in addition, is operable in the manner of a missile shield.
A further object of the present invention is to provide such a head equipment support structure system that is also operable in the manner of a ductwork support structure.
A still further object of the present invention is to provide such a head equipment support structure system that is characterized in the ease with which it may be repositioned for purposes of effecting the removal of the head of the reactor vessel.
Yet another object of the present invention is to provide such a head equipment support structure that is equally applicable for use in new installations as well as retrofit applications.
Yet still another object of the present invention is to provide such a head equipment support structure system that renders it possible through the use thereof to attain measurable cost-savings and time-savings as compared to the costs and times associated with the use of prior art forms of support structure systems.